Author Topic: Scientific study of limits to endurance  (Read 1361 times)

Scientific study of limits to endurance
« on: June 06, 2019, 08:48:59 pm »
https://www.bbc.com/news/health-48527798

I somehow felt that this would be the right place for this. (Mods move it if necessary)

Smeth

  • less Grimpeur than Whimpeur...
Re: Scientific study of limits to endurance
« Reply #1 on: June 06, 2019, 08:52:29 pm »
https://www.bbc.com/news/health-48527798

I somehow felt that this would be the right place for this. (Mods move it if necessary)
Saw it on the beeb website but can't face being limited to 4000 calories a day during events
Interesting confirmation of what we experience on multi-days.

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S2L

Re: Scientific study of limits to endurance
« Reply #2 on: June 06, 2019, 08:58:09 pm »
Dunno, ask TG what he thinks about it...  ::-)

Re: Scientific study of limits to endurance
« Reply #3 on: June 06, 2019, 09:10:26 pm »
https://www.bbc.com/news/health-48527798

I somehow felt that this would be the right place for this. (Mods move it if necessary)
Saw it on the beeb website but can't face being limited to 4000 calories a day during events
Interesting confirmation of what we experience on multi-days.

Sent from my SM-J510FN using Tapatalk

Is there a difference between what you want to take on board because it makes you feel good and what your body can really absorb and convert?

Smeth

  • less Grimpeur than Whimpeur...
Re: Scientific study of limits to endurance
« Reply #4 on: June 06, 2019, 09:17:33 pm »



Is there a difference between what you want to take on board because it makes you feel good and what your body can really absorb and convert?

Guilty as charged. I also worry about the knock and often gain weight in or after 600+ rides. I'm getting better control more recently. On WCW 600 the very fast riders seemed to eat more prudently. Obviously they are more efficient but they're really pushing out the watts. And their body fat % certainly looks lower.

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Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Scientific study of limits to endurance
« Reply #5 on: June 06, 2019, 09:35:29 pm »
Yebbut you're not limited to 4,000 calories a day unless your event lasts several months. If it's a single day event you could feasibly use 24,000, which is an awful lot of cake and beans on toast.
A cup of tea is the perfect bridge between real life and cake.

Smeth

  • less Grimpeur than Whimpeur...
Re: Scientific study of limits to endurance
« Reply #6 on: June 06, 2019, 09:42:21 pm »
Or 200 sausages.

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hellymedic

  • Just do it!
Re: Scientific study of limits to endurance
« Reply #7 on: June 06, 2019, 10:34:05 pm »
If you are not vomiting and have normal stools, you will be absorbing most of your food.
How much you can actually eat varies between individuals but can be 'trained up'
Skinny AUKs might be better at using body fat as fuel.

CrazyEnglishTriathlete

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Re: Scientific study of limits to endurance
« Reply #8 on: June 06, 2019, 10:39:43 pm »
I remember reading Robert Swan's account of his foot /manhauling journey to the South Pole "In the Footsteps of Scott".  The research their doctor ?Robert Mear had performed was that the human body would not absorb more than 4500 calories a day in the long run, and that with their planned schedule they would be expending 6500 calories a day, therefore they would have a net loss of 2000 calories a day.  Over the 70 days of the expedition this would cause a substantial weight loss (all fat burning) and so each of the participants had  aminimum weight that they had to achieve before they set off, so that they would still be in an acceptable condition at the end.

The BBC is presumably referencing some more modern research but this limit on endurance was known about 35 years ago.

If you look at Teethgrinder's data, for the year record, the challengers were trying to keep their heart rate low (<100bpm), so that they were keeping within the limit of what they could consume.  Amanda Coker is a very talented cyclist (a top level amateur USA time triallist) who picked an ideal route (almost flat, relatively sheltered, warm climate) which would have helped to cover distance with the minimum calorific expenditure.
Eddington Numbers 125 (imperial), 168 (metric) 518 (furlongs)  111 (nautical miles)

Re: Scientific study of limits to endurance
« Reply #9 on: June 06, 2019, 10:57:34 pm »
Back in the 70's / 80's Jim Curran used to go on expeditions to climb K2 and other Karakoram peaks at a deliberately overweight 17 stone.  Three months later he'd return at his optimal 10.5 stone. Climbers to the greater ranges have also known (for a similar period) about managing the difference between expenditure of energy and consumption.

quixoticgeek

  • Mostly Harmless
Re: Scientific study of limits to endurance
« Reply #10 on: June 06, 2019, 11:59:32 pm »


The before and after pictures of Ranulph Fiennes and Dr Mike Stroud, on their polar expeditions are kinda shocking. They do the whole putting on weight prior to the expedition because they know how much they are going to lose on the journey.

James Hayden has an interesting blog post about if a grand tour rider could be competitive on a race like the TCR, and he suggests that probably not, as they have so little body fat, they don't have the reserves needed. Losing 3-5kg over the course of a race is about 27000-45000kcal of energy deficit...

I'm at least 20kg overweight, that means I'm carting round about 180000kcal, or enough to do about 7200km. Or 90 days of every day life at the RDA for calories for a woman... Unfortunately it's bloody difficult to get the human body to just use it's reserves, and so while I have done 150km on a totally empty stomach[1], and a 40km -4°C ride before breakfast, neither is an experience I would call pleasant. And neither was very fast.

J

[1] adverse Entomological interaction resulted in unscheduled rapid evacuation of stomach contents via original route of ingress... After which the digestive system refused to accept further input...
--
Beer, bikes, and backpacking
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Re: Scientific study of limits to endurance
« Reply #11 on: June 07, 2019, 09:42:45 am »
Is there a difference between what you want to take on board because it makes you feel good and what your body can really absorb and convert?

There must be.

I use maybe 16,000kcal for a 24hr TT and ingest ~ 10,000kcal in that time.

It's all CHO. If I was eating the food I 'wanted' to eat, I'd not get anywhere near that amount because fats and proteins slow gastric emptying so I'd just be sick if I tried eating 10,000kcal of beer and pies :)

Gus

  • Loosing weight stone by stone
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Re: Scientific study of limits to endurance
« Reply #12 on: June 07, 2019, 12:17:00 pm »
Yebbut you're not limited to 4,000 calories a day unless your event lasts several months. If it's a single day event you could feasibly use 24,000, which is an awful lot of cake and beans on toast.

somewhere on my computer i have some older scientific studies, one of them followed a RAAM rider and monitored his energy intake and output throughout the race. He statred out using âpprox. 22.000 calories/day the first 2 days, but couldn't get his intake above 17000 calories/day. His performance level got lower and lower during the event, because he never had a chance to gain the calories he lost in the first 48 hours of the event.

S2L

Re: Scientific study of limits to endurance
« Reply #13 on: June 07, 2019, 03:11:31 pm »
He statred out using âpprox. 22.000 calories/day the first 2 days, but couldn't get his intake above 17000 calories/day. His performance level got lower and lower during the event, because he never had a chance to gain the calories he lost in the first 48 hours of the event.

Not sure about those figures... that implies he was using over 1000 Kcal per hour which is race pace and I mean proper race, not multi day race.
I would be happier with something along the lines of 600 to 700 KCal per hour and that is already pushing, probably well in excess of 20 mph on the flat

Re: Scientific study of limits to endurance
« Reply #14 on: June 07, 2019, 03:33:14 pm »
Yeah, 22,000kcal is almost certainly wrong, like me doing my 25mi pace for 24hrs. Maybe it was 22,000kj but then that's only 5258 kcal (low)

Re: Scientific study of limits to endurance
« Reply #15 on: June 07, 2019, 04:14:25 pm »
There is also a limit to how many calories you can actually absorb - I'm sure they used to say it was around 7000 calories per day.

If you use a fructose/glucose mix I think it is 90g CHO per hour = ~360 calories per hour or 8640 per day. No doubt there will be some variation between individuals but I imagine if you try to take on much more you will probably just get the trots.

Audax Ecosse - always going too far

Re: Scientific study of limits to endurance
« Reply #16 on: June 07, 2019, 04:32:43 pm »
There is also a limit to how many calories you can actually absorb - I'm sure they used to say it was around 7000 calories per day.
If you use a fructose/glucose mix I think it is 90g CHO per hour = ~360 calories per hour or 8640 per day. No doubt there will be some variation between individuals but I imagine if you try to take on much more you will probably just get the trots.

Can't find the article but Asker J talked about a female Ironman (record holder perhaps?) who raced on 120g / hr. I tried this level but it was too much and I was constantly eating during training.
90g/hr is much more doable, personally.

https://www.gssiweb.org/sports-science-exchange/article/sse-108-multiple-transportable-carbohydrates-and-their-benefits
http://www.mysportscience.com/single-post/2015/05/23/Is-more-carbohydrate-better-during-exercise-And-how-much-is-too-much


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Re: Scientific study of limits to endurance
« Reply #17 on: June 07, 2019, 04:46:51 pm »
There's a video on youtube with Andy Wilkinson being interviewed.   He recommended 1g carb/kg weight per hour.

For me this is around 60g/hr which has worked well in 12hr/24hr TTs.   I take on less during audaxes as the overall pace is a bit lower.

Re: Scientific study of limits to endurance
« Reply #18 on: June 07, 2019, 04:51:25 pm »
That's reasonable, but Asker's research (or at least his articles) indicated it's not related to body mass - hence the much smaller female Ironwoman able to race on 120g/hr

"The advice for prolonged endurance events (2.5 h or longer) is an intake of 90 g of multiple transportable carbohydrates per hour. This advice is not expressed relative to body mass because body size/mass appears to play no major role in exogenous carbohydrate oxidation."

All of this info is with the caveat that you have to train your gut to handle these high quantities of CHO and they have to use multiple transportable CHO, ie. glucose:fructose combinations. If you're only using glucose you're maxed out at around 60g/hr.

Gus

  • Loosing weight stone by stone
    • We will return
Re: Scientific study of limits to endurance
« Reply #19 on: June 07, 2019, 05:37:32 pm »
He statred out using âpprox. 22.000 calories/day the first 2 days, but couldn't get his intake above 17000 calories/day. His performance level got lower and lower during the event, because he never had a chance to gain the calories he lost in the first 48 hours of the event.

Not sure about those figures... that implies he was using over 1000 Kcal per hour which is race pace and I mean proper race, not multi day race.
I would be happier with something along the lines of 600 to 700 KCal per hour and that is already pushing, probably well in excess of 20 mph on the flat

Couldn't find the whole article, but found the abstract https://www.ncbi.nlm.nih.gov/pubmed/16037895
179.650 Kcal in the 9 days 17 hours he raced  :o
As I recall, some of the fastest riders during that periode, rode the first 48 hours without any sleep and used short stops to refuel and change clothes.

Re: Scientific study of limits to endurance
« Reply #20 on: June 07, 2019, 05:42:35 pm »
"average of 9,612+/-1,500 (7,513-12,735) kcal per day" sounds much more reasonable.

S2L

Re: Scientific study of limits to endurance
« Reply #21 on: June 07, 2019, 06:56:37 pm »
He statred out using âpprox. 22.000 calories/day the first 2 days, but couldn't get his intake above 17000 calories/day. His performance level got lower and lower during the event, because he never had a chance to gain the calories he lost in the first 48 hours of the event.

Not sure about those figures... that implies he was using over 1000 Kcal per hour which is race pace and I mean proper race, not multi day race.
I would be happier with something along the lines of 600 to 700 KCal per hour and that is already pushing, probably well in excess of 20 mph on the flat

Couldn't find the whole article, but found the abstract https://www.ncbi.nlm.nih.gov/pubmed/16037895
179.650 Kcal in the 9 days 17 hours he raced  :o
As I recall, some of the fastest riders during that periode, rode the first 48 hours without any sleep and used short stops to refuel and change clothes.

Sounds wrong and very inefficient, I use about a quarter of a million calories per year, to cover about 12,000 km

RAAM is less than 5,000, so you'd be hard pushed to use over 100,000 Kcal

Re: Scientific study of limits to endurance
« Reply #22 on: June 07, 2019, 07:29:43 pm »
That's reasonable, but Asker's research (or at least his articles) indicated it's not related to body mass - hence the much smaller female Ironwoman able to race on 120g/hr

"The advice for prolonged endurance events (2.5 h or longer) is an intake of 90 g of multiple transportable carbohydrates per hour. This advice is not expressed relative to body mass because body size/mass appears to play no major role in exogenous carbohydrate oxidation."

All of this info is with the caveat that you have to train your gut to handle these high quantities of CHO and they have to use multiple transportable CHO, ie. glucose:fructose combinations. If you're only using glucose you're maxed out at around 60g/hr.

Yeah.  I suspect I’d need to take on liquid carbs as well to get to 90g/hr.  I currently use bars and gels and then just drink water with a hydration tablet.

Re: Scientific study of limits to endurance
« Reply #23 on: June 07, 2019, 11:34:28 pm »
Liquid makes it easier but practice is the key.
When I was racing long TTs I used exclusively liquid and made sure I consumed 300 cal per hour (which was about 70g Cho and 5g protein). I trained by using the same drinks on every audax and other ride I did.  When I started focusing on ultra races I switched to bars and aim for a similar calorific intake. It's harder and I get a dirtier fuel mixture, ie more fat, and sometimes feel a bit sick. Normally it works ok, though. If carrying a few spare kg and never bonking is a measure of success, I could say it works pretty well!

Re: Scientific study of limits to endurance
« Reply #24 on: June 07, 2019, 11:42:43 pm »
This article sounds like bollocks to me. A good railway navvy in the 19th Century would take a year to train to a level where he could keep up with experienced men. Manual labour was serious then.

Quote
Deprived of modern conveniences such as the internal combustion engine and all the labour-saving technology that we take for granted, the lives of the mid-Victorians revolved around manual labour. To fuel their high levels of physical activity they required far more food than we do today; women typically consumed between 3,000 and 3,500 calories per day while men consumed 4,000 – 5,000 calories, with the navvies, who built the roads, canals and bridges that created the topology of modern Britain, hitting 6 or 7 thousand calories per day. This compares with an average of around 2,200 today, a figure that we think of as normal but which, at only a relatively small percentage over BMR, is at an historic and unhealthy low.

https://www.ifbb.org.uk/real-food/how-has-what-we-eat-changed/

There are plenty of people around with Navvy genetics, who are doomed to cycle enormous distances to keep their weight under control. Andy Wilkinson is a builder, who does a lot of labouring, Beryl Burton was an agricultural labourer, they're throwbacks to the 19th Century. In modern sports physiology we have 'rest days'. Navvies had a 'Day of Rest'; Sunday.

Modern people have trouble metabolising food because their bodies aren't used to it. Such is the nature of white-collar sport.